docs: def to_dict(self):
          """Return a dict representing the ChemicalEntity that can be read back
          using from_dict.
          
          """
          
          ret = merge_dicts(self.__attributes__, self.__relations__, self.__fields__)
          ret = {k : v.value for k,v in ret.items()}
          ret['maps'] = {k : v.value for k,v in self.maps.items()}
          return ret